Method and apparatus using deliquescent filter for separating mixture

ABSTRACT

The present invention provides a method and apparatus for separating a mixture to be separated (solid-liquid or liquid-liquid mixture) using a deliquescent filter medium. The mixture to be separated is separated into a liquid passing through a filter layer of the filter medium and a captured material captured in the filter layer.

TECHNICAL FIELD

The present invention relates to a technique for separating aliquid/liquid mixture or a liquid/solid mixture.

BACKGROUND ART

A technique for separating liquid/liquid mixtures and solid/liquidmixtures includes filtration (Perry Robert H. Perry's ChemicalEngineers' Handbook, 6th ed., pp. 19.65-19.89, 1984) (this hand book isreferred to as the “Perry document” hereinafter). In the filtration, amixture to be separated (solid-liquid mixture or liquid-liquid mixture)is supplied to a filter layer made of a porous material (diatomaceousearth), a fibrous material, or the like, and a liquid is passed throughthe filter layer due to differential pressure (such as centrifugalforce) while a solid is captured in the filter layer. Alternatively, alow-viscosity liquid is passed through the filter layer, while ahigh-viscosity liquid and/or a solid are captured in the filter layerand separated. With respect to the low-viscosity liquid and thehigh-viscosity liquid, a liquid and a liquid immiscible therewith(hereinafter referred to as an “immiscible liquid”) (a plurality ofimmiscible liquids may be contained) in a liquid-liquid mixture areregarded as the low-viscosity liquid and the high-viscosity liquid,respectively, by a relative comparison of viscosities.

1. Filtration and Recovery of Captured Material

In the filtration, it is a difficult problem to improve recovery and arecovery rate (=recovery amount/capture amount) of substances capturedin the filter layer. The filtration also includes separation by amembrane (such as ultra filtration membrane). Methods for improving arecovery rate of captured substances include a method using an organicsolvent (such as hexane) (Perry, pp. 15 1-15 20). However, this methodmay cause deterioration of the captured substances. In addition, asolvent is generally recovered by an evaporation method, therebyincreasing the cost of the method (a large quantity of heat energy isrequired for evaporating the solvent).

2. Deliquescent Filter Media

It is considered that filter crystals described below can be used asfilter media for capturing viscous solutions and solids. The filtercrystals are the followings:

a) Fine crystals (which may be grains), needle/rod-like crystals,dendrite-like crystals, or flake/plate-like crystals produced in aliquid; crystals produced by removing or scraping the crystals formed bycontact between a cooled solid material such as metal and a liquid; orcrystals by grinding (such as impact grinding using rotation centrifugalforce) or crystals by crushing after their formation.

b) Crystals produced by mixing a mother liquid in a gas bylow-temperature evaporation, heating evaporation, spraying, or liquiddropping, forming crystals by contact between the resultant mixture anda cooled solid (such as metal) or a solid (such as plastic), andremoving or scraping the crystals from the cooled solid or the solid.

c) A crystal group including the above-described crystals a) and/or b).

The filter crystals are deliquescent single crystals and/orpolycrystals. Possible substances for the filter crystals includematerials such as ice.

a) Formation of Filter Crystals in Liquid

It is known from documents below that filter crystals can be formed inliquid by rapid crystallization of single-component liquids or rapidcrystallization of multi-component liquids.

With respect to formation of ice crystals from an aqueous solution,Thijssen, H. A. C., A. Spicer ed., Applied Science Pub. LTD., London UK,p. 117-121, 1974 (hereinafter referred to as the “Thijssen document”)discloses the followings:

1. In cooling from a cooled surface (unidirectional cooling),needle-like or rod-like ice crystals having branches crossingperpendicularly to the cooled surface are formed.

2. In a liquid, an amount of fine crystals increases (the occurrencerate of crystal nuclei (fine ice) increases) with increasing coolingrate or increasing solute concentration.

3. Ice crystals increase in size over time.

With respect to freezing of water, Y. FURUKAWA and E. YOKOYAMA, JASMAVol. 21, 217-223 2004 discloses that an amount of dendrite crystalsincreases with increasing cooling rate.

In addition, PETER V. HOBBS, CLARENDON PRESS OXFORD, p. 580-581 1974discloses that dendrite crystals are easily formed from an aqueoussolution as compared with water.

Examples of materials other than water that can be used for filtercrystals of the present invention include clathrate hydrates (U.S. Pat.No. 6,237,346 B1) and the like.

U.S. patents (U.S. Pat. No. 3,845,230 and U.S. Pat. No. 3,320,153)disclose techniques in which a solid-liquid mixture or a liquid passesthrough a layer composed of ice crystals. The U.S. Pat. No. 3,845,230discloses a centrifugal dehydration (filtration) method for forming anice crystal layer using a rotating basket described below in “DetailedDescription of the Invention”. Also it is described that spherical icecrystals are formed by extending a residence time during slow freezingand that fine ice crystals are produced by shortening a residence timeduring rapid freezing. The U.S. Pat. No. 3,320,153 relates to atechnique for separating oil and a mixture of ice crystals andsolidified wax.

b) Formation of Filter Crystals in Gas

A type of formation of filter crystals in a gas includes natural snow.

It is known that filter crystals can be formed in an artificial gas asfollows: A liquid is mixed in a gas by low-temperature evaporation,heating evaporation, spraying, or liquid dropping, and the resultantmixture is put into contact with a crystal forming material or a cooledcrystal forming material to produce a liquid solidified product(artificial snow) (Mitsuo, et al. Trans. of the JSRAE, Vol. 25, pp.325-335 2008).

3. Filtration

Documents explaining a filter layer and a fluid mixture to be passedthrough the filter layer according to the present invention aredescribed below. According to these documents, the following matters arefound. 1) A filtration is considered as a method capable of separating aliquid-liquid (a high-viscosity liquid and a low-viscosity liquid)mixture by capturing the high-viscosity liquid by a crystal-filter layerand passing the low-viscosity liquid through the crystal-filter layer.2) A filtration has the function to coalesce immiscible droplets orsmall solids.

3.1 Characteristics of Filtration

a) Based on research of freeze concentration (separation between icecrystals and concentrate), the Thijssen document describes on pp.130-132 the following. In a method for separating between ice crystalsand a liquid (squeezing, centrifugal dehydration, and washing), apermeation rate of the liquid (filtrate amount per unit area and time)is inversely proportional to the viscosity of the liquid and the filterlayer thickness (filter layer passage distance of a mixture to beseparated) and is proportional to the square of a mean crystal diameter.The Thijssen document also describes that in centrifugal filtration ofice crystals and a liquid, the amount of a liquid remaining in thefilter layer is proportional to the viscosity of the liquid, and thatthe amount of remaining liquid decreases with increasing centrifugaleffect (G).

b) In regard to centrifugal filtration, Masao et al., AlChEJ, Vol. 33,pp. 109-120 1987 and Perry document 19.96-19.103 describe the following:The permeation flow rate decreases as the viscosity of a liquidincreases and the filter layer thickness increases (the filter layerpassage distance of a mixture to be separated increases). In addition,the permeation flow rate increases with increasing centrifugal effect(G) and with increasing rotation time.

3.2 Coalescing Function of Filtration

In Spielman, L. A. and Goren, S. L., Ind. Eng. Chem., Vol. 62, No. 10,p. 10-24 (1970), U.S. Pat. No. 4,335,001, and S. D. Rege, H. S. Fogler,AlChE Vol. 34, 1988, it is described that the filtration has thefunction to coalesce small solids or immiscible droplets (such asemulsion) in a mixture to be separated.

In the document of Spielman, L. A. and Goren, it is also described thatthe larger solids or droplets (the larger aggregates), the more easilythe solids or droplets are captured in a filter layer.

In the present invention, considering the coalescing function(facilitating subsequent separation) of the filter layer, the coalescingfunction may be used as pre-treatment for separation of the mixture tobe separated regardless of the presence of capture in the filter layer.

The document of Spielman and Goren further describes that a differencein permeability occurs between a high-viscosity liquid and alow-viscosity liquid when a mixture of these liquids is passed throughthe filter layer.

SUMMARY OF INVENTION

The present invention provides a method and an apparatus using adeliquescent filter medium for separating a mixture to be separated(solid-liquid or liquid-liquid mixture). The mixture to be separated isseparated into a liquid passing through a crystal-filter layer which ismade of the deliquescent filter medium and a captured material capturedin the crystal-filter layer.

The present invention relates to a method having advantages such as thefollowings:

1. A filter medium and a captured material are separated by melting thefilter medium. Thus, the capturing material and the captured materialare easily separated.

2. Further, when a low-temperature material such as ice, snow, or thelike is used as the filter medium, corruption and deterioration can bedelayed in treatment of natural products and the like.

3. In a preferred embodiment of the present invention, components with asmall difference in specific gravity in a mixture to be separated canalso be separated.

Typical examples of a method using a deliquescent filter medium of thepresent invention are described below.

A method according to the present invention is a method for separating amixture to be separated including a) a step of forming mother liquidcrystals from a mother liquid, b) a step of forming deliquored filtercrystals by deliquoring the mother liquid crystals, c) a step of forminga crystal-filter layer of the deliquored filter crystals and supplying amixture to be separated to a surface of the formed crystal-filter layerto separate the mixture to be separated into a passing liquid passingthrough the crystal-filter layer and a crystal-filter layer supportingwall having holes, and a captured material captured in thecrystal-filter layer, d) a step of melting the crystal-filter layeramong the crystal-filter layer and the captured material captured in thecrystal-filter layer, and e) a step of separating, by gravity settling,the melted crystal-filter layer and the captured material captured inthe crystal-filter layer.

Another method according to the present invention is a method forseparating a mixture to be separated including a) a step of formingfilter crystals from a mother liquid, b) a step of forming acrystal-filter layer of the filter crystals and supplying a mixture tobe separated to a surface of the formed crystal-filter layer to separatethe mixture to be separated into a passing liquid passing through thecrystal-filter layer and a crystal-filter layer supporting wall havingholes, and a captured material captured in the crystal-filter layer, c)a step of melting the crystal-filter layer among the crystal-filterlayer and the captured material captured in the crystal-filter layer,and d) a step of separating, by gravity settling, the meltedcrystal-filter layer and the captured material captured in thecrystal-filter layer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a system including a crystal generator, a deliquoringdevice, a separator, and a melting tank according to an embodiment ofthe present invention. In FIG. 1, separation after melting a capturingcrystal-filter layer is performed by a gravity settling separationmethod for a liquid-liquid mixture. In addition, a case where a removedliquid and/or a melt produced in the gravity settling separation methodare used as a mother liquid is shown by dotted lines.

FIG. 2 shows a system including a crystal generator, a separator, and amelting tank according to an embodiment of the present invention. InFIG. 2, separation after melting a capturing crystal-filter layer isperformed by a gravity settling separation method for a solid-liquidmixture. In addition, a case where a melt produced in the gravitysettling separation method is reused as a mother liquid is shown bydotted lines.

FIG. 3 is a schematic drawing of an in-liquid rotating drum-type crystalgenerator.

FIG. 4 is a schematic drawing of an in-gas low-temperatureevaporation-type crystal generator.

FIG. 5 is a schematic sectional view showing an operation of aconveyor-type deliquoring device.

FIG. 6 is a schematic sectional view showing an operation of a filtercloth inverting-type separator. FIG. 6A shows an operation during supplyof filter crystals, FIG. 6B shows an operation during supply of amixture to be separated, and FIG. 6C shows an operation during dischargeof a capturing crystal-filter layer.

FIG. 7 is a schematic sectional view showing an operation of a drumfiltration-type separator.

FIG. 8 shows conditions of holes of a crystal-filter layer supportingwall having holes. FIG. 8A is an arrangement of the holes in a surfaceof the supporting wall, and FIG. 8B is an enlarged sectional view of thesurface of the supporting wall and a capturing crystal-filter layer.

FIG. 9 is a schematic sectional view showing a disk-type centrifugalseparator.

DETAILED DESCRIPTION OF THE INVENTION 1. Outlines of Apparatuses

Outlines of apparatuses constituting a system are described.

FIGS. 1 and 2 show typical examples of a system for separating a mixtureto be separated using a deliquescent filter medium. A system shown inFIG. 1 is a system including a crystal generator 2, a deliquoring device3, a separator 6, and a melting tank 8. A system shown in FIG. 2 is asystem including a crystal generator 2, a separator 6, and a meltingtank 8. In the present invention, such a system may be installed in acooling environment such as a cooling room or chamber.

Each of the apparatuses constituting the systems is described below.

1) Crystal Generator 2

The crystal generator 2 is an apparatus for forming mother liquidcrystals 2 a. The crystal generator 2 produces the mother liquidcrystals 2 a by cooling a mother liquid 1 a.

The mother liquid crystals 2 a are crystals, a mixture of crystals andthe mother liquid 1 a, filter crystals 100, or a mixture of the filtercrystals 100 and the mother liquid 1 a. When the mother liquid 1 a is amulti-component liquid, a liquid in the mixture has a soluteconcentration different from the mother liquid 1 a.

The mother liquid crystals 2 a are transferred to the deliquoring device3, the separator 6, or a deliquoring separator described below.

2) Deliquoring Device 3

The deliquoring device 3 is an apparatus that forms deliquored filtercrystals 3 a.

The mother liquid crystals 2 a are deliquored by passing through amother liquid crystal supporting wall (a basket- or drum-like wall, afilter cloth, a screen, or the like) having holes in the deliquoringdevice 3 (due to centrifugal force, differential pressure, orcombination thereof). Alternatively, the deliquoring is combined withhigh-speed rotation crystal impact (ejection) grinding, crystalcrushing, or the like to form the deliquored filter crystals 3 a(removed liquid is referred to as a “deliquored liquid 4 a”). Thedeliquored filter crystals 3 a are filter crystals, or a mixture offilter crystals and the mother liquid 1 a.

The deliquoring efficiency may be low.

The deliquored liquid 4 a is transferred to a deliquored liquid tank 4.

The deliquored liquid 4 a may be reused as the mother liquid 1 a (to thecrystal generator 2). Reuse of the deliquored liquid 4 a has thepossibility as a supply for a new mother liquid 1 a to the mother liquidtank 1, energy for cooling (or heating) the mother liquid 1 a, orlow-cost, energy-saving method and apparatus due to the reduction ofdisposal of the deliquored liquid 4 a and the like. When the motherliquid 1 a is a multi-component liquid, the deliquored liquid 4 a has asolute concentration different from the mother liquid 1 a. In this case,the deliquored liquid 4 a may be adjusted to the same soluteconcentrated as the mother liquid 1 a.

The deliquored filter crystals 3 a are transferred to the separator 6.

3) Separator

The separator 6 is an apparatus that separates a mixture to be separated(liquid-liquid, solid-liquid) by a crystal-filter layer 6 a and acrystal-filter layer supporting wall 600 having holes.

The crystal-filter layer supporting wall 600 having holes is a basket-or drum-like supporting wall, a filter cloth, a screen, or the like.

The deliquored filter crystals 3 a from the deliquoring device 6 or themother liquid crystals 2 a from the crystal generator 2 are transferredto the separator 6, forming a filter layer (hereinafter the“crystal-filter layer 6 a”) including the crystals as a filter medium inthe separator. Natural snow or the like may be transferred as the filtercrystals to the separator. The deliquored filter crystals 3 a, themother liquid crystals 2 a, or the filter crystals 100, which aretransferred to the separator, may be accompanied by a liquid.

Next, a mixture 5 a to be separated is supplied to a surface of thecrystal-filter layer 6 a (in which centrifugal force, differentialpressure, or combination thereof is exerted in the separator 6).

The mixture 5 a to be separated is separated into a passing liquid 7 awhich passes through the crystal-filter layer 6 a and the crystal-filterlayer supporting wall having holes, and a captured material captured inthe crystal-filter layer.

When the mixture to be separated is a liquid-liquid mixture, alow-viscosity liquid (an aqueous solution or the like) in the mixture tobe separated passes through the crystal-filter layer 6 a and thecrystal-filter layer supporting wall 600 having holes, and discharged tothe outside of the crystal-filter layer supporting wall, while ahigh-viscosity liquid 8 b (oil or the like) is captured in thecrystal-filter layer.

On the other hand, when the mixture 5 a to be separated is asolid-liquid mixture, a liquid in the mixture to be separated passesthrough the crystal-filter layer 6 a and the crystal-filter layersupporting wall 600 having holes, and discharged to the outside of thecrystal-filter layer supporting wall, while a solid 8 c is captured inthe crystal filter-layer 6 a. Further, when a liquid in a solid-liquidmixture includes a liquid and an immiscible liquid like in theliquid-liquid mixture, the high-viscosity liquid 8 b may be or not becaptured in the crystal-filter layer according to applications of thepresent invention.

Further, for the purpose of separating a plurality of immiscible liquidsin liquid-liquid and liquid-solid mixtures, the present invention may beused as a method and apparatus for separating a high-viscosity liquidand a low-viscosity liquid in immiscible liquids on the basis of thesame principle (a difference in viscosity between immiscible liquids) asin the liquid-liquid mixture.

Also, the present invention may be used as a separation (wintering orthe like) method and apparatus utilizing a difference in freezing point.

In addition, the mother liquid crystals 2 a formed by the crystalgenerator 2 may be transferred to a deliquoring separator. Thedeliquoring separator continuously performs the operations of thedeliquoring device 3 and the separator 6 in a single apparatus. Through(a) a step of supplying mother liquid crystals, (b) a deliquoring step,(c) a step of supplying the mixture to be separated, and (d) a step ofdischarging a capturing crystal-filter layer (described below), in thedeliquoring separator, a low-viscosity liquid in the mixture 5 a to beseparated which is supplied in step (c) passes through thecrystal-filter layer and the crystal-filter layer supporting wall havingholes, while a high-viscosity liquid 8 b and/or a solid are captured inthe crystal-filter layer.

In the present invention, before supply, the temperature of the mixture5 a to be separated may be decreased to produce a solidified matter (thesame material as the filter crystals, solidified oil, or the like) inthe mixture 5 a to be separated. An example of the present inventionmethod where a solidified matter in the mixture 5 a to be separated isthe filter crystal is described with reference to a filter aid.

After the above-described operations, the liquid 7 a passing through thecrystal-filter layer 6 a and the crystal-filter layer supporting wall600 is transferred to a passing liquid tank 7. In addition, thecrystal-filter layer 6 a and the captured material are transferred to anapparatus (melting tank 8 or the like) for melting the crystal-filterlayer.

The captured material includes the high-viscosity liquid 8 b and/or thesolid 8 c captured in the crystal-filter layer 6 a. Hereinafter, thecrystal-filter layer 6 a containing the captured material is referred toas a “capturing crystal-filter layer 6 b”.

In addition, in the present invention, the same as the passing liquid 7a or components thereof may be captured in the capturing crystal-filterlayer 6 b within a range in which the intended purpose of the system ofthe present invention can be achieved.

4) Melting of Crystal-Filter Layer

The crystal-filter layer in the capturing crystal-filter layer is meltedwith an apparatus for melting the crystal-filter layer (hereinafter, amaterial containing a melt of the crystal-filter layer as a maincomponent is referred to as a “melt”). The melting is performed byheating (due to a difference in temperature between the inside andoutside of a heater, a melting device, or the like).

During melting of the crystal-filter layer, a solid (solidified oil orthe like) in the capturing crystal-filter layer may be or not moltenaccording to the intended purpose of the system according to the presentinvention.

The separated melt 8 a may be used (reused) as the mother liquid 1 a ofthe crystal generator 2. In this case, reuse has the possibility as asupply for a new mother liquid 1 a to the mother liquid tank 1, energyfor cooling (or heating) the mother liquid 1 a, or a low-cost,energy-saving method and apparatus due to the reduction of disposal ofthe melt 8 a and the like. Also, the reuse of the melt 8 a has thepossibility of decreasing the filter medium cost for changing the filtermedium and/or the cost for treating (disposal or the like) the filtermedium after use as compared with conventional filtration.

2. Details of Apparatus

Details of the apparatuses constituting the system are described below.

1) Crystal Generator

The crystal generator is an in-liquid or in-gas type apparatus. In thein-liquid type apparatus, crystals are generated (solidification of amother liquid) using a cooled solid (metal or the like) or a cooledfluid (gas, liquid) (brought into contact with a mother liquid) in amother liquid, and the crystals are removed or scraped. In the in-gasapparatus, a mother liquid is mixed in a gas by low-temperatureevaporation, heating evaporation, spraying, or liquid dropping, theresultant mixture is brought into contact with a cooled solid (metal orthe like) or a solid (plastic or the like) to produce crystals(solidification of the mother liquid), and the crystals are removed orscraped.

In-liquid type apparatuses for generating crystals on a cooled solidinclude a rotating drum type 21 (FIG. 3), an internally scraping drumtype, and the like. Among these, the internally scraping drum typeincludes an internally scraping heat exchanger type, an annular gapscraping type, an auger type, and the like. The general characteristicsof these in-liquid type apparatuses are described in the documentsbelow. The rotating drum type is described in U.S. Pat. No. 6,233,953 B1and Toyohiko, O., Dechema-Monographien, BAND 47, pp. 815-821, 1962. Theinternally scraping heat exchanger type is described in the Thijssendocument, the annular gap scraping type is described in Frytherm:Company Frymakoruma, Neuenburg. Germany, and the auger type is describedin U.S. Pat. No. 4,497,184.

The cooled solid is generally cooled using a refrigerator. However, whenthe mother liquid is at high temperature, the cooled solid may be cooledby fan cooling, water cooling, or the like without using a refrigerator.When the cooled solid is cooled with a refrigerator, a cooling mediummay be either refrigerant or brine.

In the in-liquid type apparatus for producing crystals (solidificationof a mother liquid) using a cooling fluid (gas or liquid), examples of acooling gas include normal butane gas and iso-butane gas (Herbert, F.,Advance in Chemistry Series, No. 27, pp. 82-89 1960), and examples of acooling liquid include hydrofluoroether (inert antifreezing liquid) (3MCo., USA).

The in-gas type apparatus includes an evaporation type, a spraying type,a dropping type, and the like, and methods thereof include alow-temperature evaporation method, a heating evaporation method, anultrasonic method, a centrifugal method, a high-pressure sprayingmethod, a two-fluid spraying method, and the like. The generalcharacteristics of these in-gas apparatuses are described, together withthe low-evaporation method (FIG. 4), in Mitsuo, et al. Trans. of theJSRAE, Vol. 25, pp. 325-335 2008. The term “low-temperature evaporation”represents that a liquid of 0° C. or more (boiling point or less) isbrought into contact with a gas of 0° C. or less to mix vapor and/orfine droplets of the liquid in the gas.

Also, an apparatus of a type in which the mother liquid 1 a is dispersedon a cooled surface to produce a solidified matter, which is thenscraped, can be used as the crystal generator 2.

The crystal generator 2 may be a crushing-type apparatus in which largeor small crystal lumps (lamps of ice or the like) are crushed.

The mother liquid 1 a may be continuously or discontinuously supplied ina necessary amount to the crystal generator 2 from the mother liquidtank 1. The mother liquid temperature in the mother liquid tank 1 may becontrolled to a necessary temperature by a heater or the like.

The shape and size of crystals produced by the crystal generator areadjusted by controlling the temperatures of the cooled solid, a solid,or the cooled fluid (gas or liquid) used for forming crystals(solidification of the mother liquid) in the crystal generator, themoving velocity of the cooled solid, a solid, or the cooled fluid (gasor liquid), the removal or scraping rate of crystals, and the like.Devices for moving or scraping crystals include a rotating brush, ascraper, a gas spray type device, and the like.

2) Deliquoring Device 3, Separator 6, and Deliquoring Separator

Any one of the deliquoring device 3, the separator 6, and thedeliquoring separator can use methods and apparatuses using variousfiltration techniques (gravitation, pressure application, and pressurereduction) including centrifugal filtration (Perry document, pp.19.65-19.103).

Among the various filtration techniques, a centrifugal method (Perrydocument, pp. 19.96-19.100) using a rotating basket as thecrystal-filter layer supporting wall 600 having holes and a centrifugalmethod (Perry document, p. 19.79) using a rotating drum as acrystal-filter layer supporting wall having holes are described below.

The crystal-filter layer supporting wall have many or plural holes whichmay be elongated holes.

The centrifugal method uses a discontinuous or continuous apparatusdescribed below. Discontinuous types include a filter cloth invertingtype 61 (FIG. 6), an automatic batch type, a bottom discharge type, andthe like, and continuous types include a conveyor type 31 (FIG. 5), anextrusion type, a conical basket type, and the like.

The general characteristics of these apparatuses are described in thedocuments below. The filter cloth inverting type 61 (FIG. 6) isdescribed in U.S. Pat. No. 7,168,571 B2. The automatic batch type, thebottom discharge type, the conveyor type 31 (FIG. 5), the extrusion type(pusher), and the conical basket type are described in Zeitsch p.509-530 and the Perry document, p. 19.96-19.100. Further, “Dehydrator”(SAITO SEPARATOR LIMITED, Japan) is the conveyor type 31 (FIG. 5), andTANABE WILLTEC INC Japan has the extrusion type. In the conveyor typeand the extrusion type, rotating baskets include a vertical type and ahorizontal type, and the shapes of the baskets include a drum shape anda conical shape.

On the other hand, the drum filtration method includes a pressuremethod, a pressure reduction method (FIG. 7), and a combination thereof(Perry document).

The drum filtration method can use a crystal generator for producingfilter crystals in a liquid tank in which a drum is immersed, thecrystal generator and a deliquoring device, or an apparatus used as thecrystal generator, a deliquoring device, and a separator. In this case,as means for generating filter crystals in the liquid tank, a crystalforming cooled surface and a cooled surface scraping blade are providedin the liquid tank, or a cooled gas or an antifreezing liquid isintroduced into the liquid tank.

2.1) Crystal-Filter Layer Supporting Wall Having Holes

When the crystal-filter layer supporting wall 600 having holes is usedin the separator 6 or the deliquoring separator, the average distancebetween the holes (between the hole outer edges) of the supporting wall600 is preferably longer than the average thickness (the distancebetween the surface of the filter layer and the wall surface having thehole) of the filter layer to which the mixture 5 a to be separated isbeing supplied. In this case, the total opening area of the holes of thesupporting wall surface having holes is smaller than the wall surfacearea excluding the opening area of the holes of the wall surface havingholes.

This is clearly explained with reference to FIG. 8. FIG. 8 shows anexample of a relation between a crystal-filter layer and acrystal-filter layer supporting wall 600 having holes in the case of thebasket-type crystal-filter layer supporting wall 600 having holes. FIG.8A shows an example of an arrangement of holes of the supporting wallsurface. FIG. 8B is a sectional view of the supporting wall surface andthe capturing crystal-filter layer 6 b when the mixture 5 a to beseparated is supplied to the crystal-filter layer using the supportingwall surface. In FIG. 8A, L1 and L2 each denote the distance between theholes of the supporting wall surface. On the other hand, in FIG. 8B, L0denotes the average thickness of the capturing crystal-filter layer towhich the mixture to be separated is being supplied. The abovedescription represents that the average distance L12 (=(L1+L2)/2)between the holes of the supporting wall surface is longer than L0(L12>L0).

The conditions of the supporting wall surface having the holes bringabout the following phenomena:

1. The flow rate and distance of the mixture to be separated, which issupplied to the surface of the filter layer, along the supporting wallsurface (after flowing through the filter layer from the filter layersurface and reaching the supporting wall surface) are increased. Thisincreases the average flow distance of the mixture to be separated (perunit volume) in the filter layer.

2. The crystal-filter medium is compressed to the supporting wallsurface due to differential pressure (centrifugal force or the like).Therefore, after reaching the supporting wall surface from the filterlayer surface (without escaping), the mixture to be separated at theabove-described flow rate is forced to be moved along the supportingwall surface through the gap between the supporting wall surface and thecrystal-filter media, and through the crystal-filter media near thesupporting wall surface, the gap being narrowed by compression.

These phenomena significantly increase the capture rate of materialscaptured in the crystal-filter layer (=amount of materials captured incrystal-filter layer/amount of crystal-filter layer/supply amount ofmixture to be separated). This indicates that the amount of thecrystal-filter medium for the desired capture rate of the separator orthe deliquoring separator can be decreased. In addition, the phenomenahave the possibility of enhancing the effect of coalescing immiscibledroplets and/or fine solids in the mixture to be separated.

2.2) Others

The mother liquid crystals 2 a, the deliquored filter crystals, or thefilter crystals are preferably supplied to the deliquoring device 3, theseparator 6, and the deliquoring separator using a screw feeder or atube conveyor.

In addition, the mixture 5 a to be separated is preferably supplied tothe crystal-filter layer in the separator or the deliquoring separatorby spraying.

When the centrifugal method is used in the deliquoring device 3, theseparator 6, and the deliquoring separator, a screen, a filter cloth, orthe like, which rotates together with a basket, may be provided insidethe basket. When the drum filtration method is used, a screen, a filtercloth, or the like, which rotates together with a drum, may be providedoutside the drum.

The shape and size of the deliquored filter crystals 3 a produced byusing the centrifugal method in the deliquoring device are preferablycontrolled by selecting the conditions such as the amount of the motherliquid crystals 2 a supplied, the discharge rate of the deliquoredfilter crystals, the rotational speed of the basket, and the likeaccording to purposes of use of the system.

Besides the conditions of the crystal-filter layer supporting wall, thepreferred operation conditions of the separator and the deliquoringseparator are preferably selected so as to increase the capture rates bythe crystal-filter layer. The operation conditions include the supplyamounts and supply rates of the mother liquid crystals 2 a, thedeliquored filter crystals, the filter crystals, and the mixture 5 a tobe separated, the differential pressure (centrifugal force or the like)of the crystal-filter layer, and the like. When the separator or thedeliquoring separator using the centrifugal method is used forseparating a liquid-liquid mixture, the time required for one filtrationis preferably short (several seconds or minutes) in order to increasethe capture rate of a high-viscosity liquid captured in thecrystal-filter layer (to decrease the discharge of the capturedhigh-viscosity liquid from the filter layer). The “time required for onefiltration” represents the time required from supply of the mixture tobe separated to the crystal-filter layer to discharge of thecrystal-filter layer from the basket.

In the present invention, the filter crystals may be used as a filteraid in the separator 6 and the deliquoring separator (pre-coating methodor body feed method) (Perry 19.85).

3) Melting of Crystal-Filter Layer

After the above-described operations, the liquid 7 a passing through thecrystal-filter layer and the crystal-filter layer supporting wall istransferred to the passing liquid tank 7. The crystal-filter layer ofthe capturing crystal-filter layer is melted using a crystal-filterlayer melting device. The melting may be performed by the melting tank 8or a system including the heater or the like provided in the coursethereof without using the melting tank. Further, the melting may beperformed in the separator. When the melting is performed in theseparator, the melting may be accompanied with gravity settlingseparation.

After the melting, the mixture can be separated (into the melt, thehigh-viscosity liquid, and solids) by a gravity settling separationmethod (gravity separation due to a difference in specific gravity), adisk-type centrifugal separation method (19.92-19.94), a drum-typecentrifugal separation method, a continuous decanter separation method(19.94), or a method and apparatus using a membrane, a filter(19.65-19.89), a coalescer, or the like (Perry).

When the melting tank 8 is used, the gravity settling separation methodcan be performed in the tank.

The melt 8 a, the low-viscosity liquid, the high-viscosity liquid 8 b,and the solid 8 c separated by the above-described separation techniquemay be contaminated with materials contained in the mixture to beseparated and/or in the melt (in amounts within a range in which theobject of the preset invention can be achieved). In the wholedescription of this patent, even when the melt 8 a, the low-viscosityliquid, the high-viscosity liquid 8 b, and the solid 8 c separated bythe system of the present invention are contaminated with othermaterials (in amounts within a range in which the object of the presetinvention can be achieved), the same expression (the melt 8 a, thelow-viscosity liquid, the high-viscosity liquid 8 b, and the solid 8 c)is used.

4) System

The crystal generator 2, the deliquoring device 3, the separator 6, thedeliquoring separator, the crystal-filter layer melting device, and thedevice for separating the mixture after separation may be used in anyone of the above-described combinations.

The combination may be used as pre-treatment means for theabove-described various separation means such as the disk-typecentrifugal separation method, the drum-type centrifugal separationmethod, the continuous decanter separation method, and a method andapparatus using a membrane, a filter, a coalescer, or the like. Forexample, the disk-type centrifugal separation method may be used forincreasing the purity of a material separated from the mixture to beseparated by the gravity settling separation method or the purity of thepassing liquid passing through the crystal-filter layer supporting wall.Further, the separation means may be used for separating a mixturecontaining a mixture in the passing liquid tank and a capturingcrystal-filter layer mixture after melting of the crystal-filter layer.

The disk-type centrifugal separation method includes applying (strong)centrifugal force, which is produced by a high-speed rotor (separationdisk), to a mixture to be separated, thereby causing a difference inmovement velocity between components in the mixture to be separated andseparating the components. Therefore, the separating ability isproportional to a difference in specific gravity between a dispersionmedium and an immiscible liquid in the dispersion medium and solid inthe mixture to be separated, and is reversely proportional to theviscosity of the dispersion medium. This technique is well known as aseparation technique for liquid-liquid (light liquid and heavy liquid)and solid-liquid (solid and liquid or solid, light liquid, and heavyliquid). The structure and principle of the technique of disk-typecentrifugal separation method (Disk-centrifuge) are described in, forexample, the Perry document, p. 19.89-103. FIG. 9 is a schematicsectional view showing an example of the disk-type centrifugal separatordescribed in the document.

The system of the present invention may be a system for continuoustreatment or batch treatment of the mixture 5 a to be separatedaccording to purposes of use. In addition, the system and the method maybe various sizes according to purposes of use.

3. Preferred Modes of System

Preferred modes 1 and 2 of the system are described below.

1) Preferred Mode 1

Preferred mode 1 (FIGS. 1, 3, 5, and 6) relates to a system includingthe crystal generator 2, the deliquoring device 3, the separator 6, andthe melting tank 8. In the preferred mode 1, the crystal generator 2 isthe in-liquid rotating drum type 21 (FIG. 3), the deliquoring device 3is a centrifugal conveyor type (FIG. 5), the separator 6 is acentrifugal filter cloth inverting type (FIG. 6), the crystal-filterlayer is melted in the melting tank 8, and a mixture after melting (orduring melting) is separated by the gravity settling separation method.

In addition, the mother liquid 1 a is a NaCl solution (sterilizedseawater), and the filter crystals are ice crystals. The mixture to beseparated is a liquid-liquid mixture.

The mother liquid 1 a is transferred from the mother liquid tank 1 tothe in-liquid rotating drum-type crystal generator 21 (FIG. 3) describedbelow.

In this mode, the rotating drum-type crystal generator 21 (FIG. 3)includes a rotating drum 211, a rotating drum mother liquid tank 212,and a rotating drum scraping blade 213. The mother liquid 1 a istransferred to the rotating drum mother liquid tank 212. A refrigerantflows on the back of the outer surface of the rotating drum. When alower portion of the rotating drum 211 is immersed in the mother liquid1 a in the rotating drum mother liquid tank 212, crystals are producedon the outer surface of the drum, and thus the mother liquid crystals 2a are formed on the outer surface of the drum with rotation of therotating drum 211. The mother liquid crystals 2 a formed on the outersurface of the drum are continuously separated from the outer surface ofthe rotating drum with the rotating drum scraping blade 213 providednear the outer surface of the drum. The mother liquid crystals 2 a are amixture of the crystals and the mother liquid.

The mother liquid crystals 2 a formed by the crystal generator 2 aretransferred to the conveyor-type deliquoring device 31 (FIG. 5) disposedbelow the crystal generator 2.

In this mode, the conveyor-type deliquoring device 31 operates asdescribed below. In this case, a basket 310 having holes is a verticaltype with a conical shape widening upward.

(a) The mother liquid crystals 2 a are introduced from the crystalgenerator 2 to the bottom of the rotating basket 310 having holes. Thecharged mother liquid crystals 2 a receive centrifugal force of therotating basket 310 having holes and diffuse on the inner wall of thebasket 310. The diffused mother liquid crystals 2 a are deliquored byrotation centrifugal force of the basket 310 while being moved upwardlyon the inner wall of the rotating basket by a screw-shaped scrapingblade 311 which rotates (at a differential rate from rotation of thebasket) near the inner surface of the basket 310. The deliquored filtercrystals 3 a are discharged from an outlet in an upper portion of thebasket. The discharged deliquored filter crystals 3 a are placed in adeliquored filter crystal tank disposed below the deliquoring device 31.On the other hand, the deliquored liquid 4 a is transferred to thedeliquored liquid tank 4. The deliquored liquid 4 a in the deliquoredliquid tank 4 is transferred to the mother liquid tank 1 afteradjustment of the concentration and is reused as the mother liquid 1 a.

The deliquored filter crystals 3 a in the deliquored filter crystal tankare transferred to the filter cloth inverting type separator 61 (FIG. 6)by a screw feeder.

In this mode, the filter cloth inverting type separator operates asdescribed below. The general characteristics of the filter clothinverting type separator are described in U.S. Pat. No. 7,168,571 B2.

(a) The deliquored filter crystals 3 a in the deliquored filter crystaltank are transferred to a filter cloth 612 (the filter cloth rotatestogether with a basket) attached to the inner side of a rotating basket(crystal-filter layer supporting wall having holes) 611 by a screwfeeder 613. The transferred deliquored filter crystals 3 a form thecrystal-filter layer 6 a on the filter cloth (FIG. 6 a).

(b) The mixture 5 a to be separates is sprayed on the surface of theformed rotating crystal-filter layer 6 a through a supply pipe 614 forthe mixture to be separated. The low-viscosity liquid in the sprayedmixture 5 a to be separated passes through the crystal-filter layer andthe crystal-filter layer supporting wall having holes, while thehigh-viscosity liquid 8 b is captured in the crystal-filter layer (FIG.6 b).

(c) The supply of the mixture 5 a to be separated is stopped. Then, thecapturing crystal-filter layer 6 b is separated from the filter cloth(due to centrifugal force) by inverting (turning inside out) the filtercloth 612 among the rotating basket 611 and the filter cloth 612. Theseparated capturing crystal-filter layer 6 b is discharged from thebottom of the separator 61 (FIG. 6 c).

After the above-described operations, the passing liquid 7 a(low-viscosity liquid) passing through the crystal-filter layer and thecrystal-filter layer supporting wall having holes is transferred to thepassing liquid tank 7. The capturing crystal-filter layer 6 b istransferred to the melting tank 8. The crystal-filter layer is melted byheating (heater) in the melting tank 8. The mixture heated in themelting tank 8 is separated into the high-viscosity liquid 8 b and themelt 8 a due to a difference in specific gravity (gravity settlingseparation).

2) Preferred Mode 2

Preferred mode 2 (FIGS. 2, 4, and 7) relates to a system including thecrystal generator 2, the separator 6, and the melting tank 8. In thepreferred mode 2, the crystal generator 2 is an in-liquidlow-temperature evaporation type 22 (FIG. 4), the separator 6 is areduced-pressure drum filtration type 62 (FIG. 7), the crystal-filterlayer is melted in the melting tank 8, and a mixture after melting (orduring melting) is separated by the gravity settling separation method.

In addition, the mother liquid 1 a is water, and the filter crystals areice crystals. The mixture to be separated is a solid-liquid mixture.

In this mode, the low-temperature evaporation-type crystal generator 22includes a humidifier 221, a rotary ventilation filter 222, a crystalscraping device 223, and a cooling chamber 224. The operations thereofare as follows.

A gas is cooled in the cooling chamber 224. The cooled gas is introducedinto the humidifier 221 by a fan 226. The cooled gas introduced into thehumidifier 221 is mixed with a mother liquid vapor (and/or finedroplets) evaporated from a mother liquid 1 a at a temperature of 40° C.The cooled gas mixed with the mother liquid 1 a is introduced into therotary ventilation filter 222 on which crystals are produced to formfilter crystals 100 (solidification of the mother liquid 1 a). Thecrystals formed on the ventilation filter 222 are removed with thecrystal scraping device 223. The cooled gas (which may contain anunsolidified mother liquid) passing through the ventilation filter 222is returned to the cooling chamber 224. The cooled gas (and theunsolidified mother liquid) is circulated by the above-described step.

The rotary ventilation filter 222 is made of a gas-permeable materialsuch as synthetic resin fibers. The cooling chamber 224 is provided witha cooler and also provided with the function to control the temperatureof cold air to the ventilation filter 222. The mother liquid 1 a in thehumidifier 221 is supplied from a mother liquid tank 1, and the motherliquid is controlled to a necessary temperature by a heater. The crystalscraping device 223 is a scraper provided near the ventilation filter222.

The filter crystals 100 formed in the crystal generator 22 aretransferred to a crystal reservoir 623 of the drum filtration-typeseparator 62 (FIG. 7) by a screw feeder 228.

In this mode, the drum filtration-type separator 62 (FIG. 7) is asfollows: The drum filtration-type separator 62 (FIG. 7) includes arotating drum (crystal-filter layer supporting wall having holes) 621,the crystal reservoir 623, and a drum scraping blade 622. In addition,pluralities of small chambers 624 communicating with the holes of thedrum are provided on the back of the surface material of the rotatingdrum. Each of the small chambers 624 is connected to a centralreduced-pressure chamber 626 through a pipe 625. The drumfiltration-type separator operates as described below. The filtercrystals 100 formed in the crystal generator 22 are transferred to thecrystal reservoir 623 by the screw feeder 228. The outer surface 621 ofthe rotating drum 621 passes through the crystal reservoir 623, and thenfilter crystals 100 are adhered on the outer surface of the drum by areduced pressure of holes on the drum 621, thereby forming acrystal-filter layer 6 a. The mixture 5 a to be separated is sprayed onthe crystal-filter layer 6 a formed from the crystal reservoir 623 byrotation of the drum 621. A liquid in the sprayed mixture 5 a to beseparated passes through the crystal-filter layer 6 a and thecrystal-filter layer supporting wall 621 having holes due to the holesof the drum under reduced pressure, while a solid 8 c is captured in thecrystal-filter layer. The capturing crystal-filter layer 6 b isseparated, by rotation of the drum 621, from the outer surface of thedrum 621 with the drum scraping blade 622 provided near the outersurface of the drum. The separated capturing crystal-filter layer 6 bfalls on a capturing crystal layer receiver 627. The crystal-filterlayer in the capturing crystal-filter layer 6 b is melted with a heater628 in the capturing crystal layer receiver 627. The melted mixture istransferred to a gravity settling separation tank disposed below thecapturing crystal layer receiver 627 and is separated into the solid 8 cand the melt 8 a due to a difference in specific gravity in the gravitysettling separation tank. On the other hand, the passing liquid 7 a(liquid) passing through the crystal-filter layer 6 a and thecrystal-filter layer supporting wall 621 having holes enters the smallchambers 624 and then enters the central reduced-pressure chamber 626from the small chambers 624 through the pipes 625, and is introducedinto the passing liquid tank 7 outside the drum.

INDUSTRIAL APPLICABILITY

The present invention is suitable for a case in which ice is used asfilter crystals, and a natural product (mixture of an aqueous solutionand oil or solid, or mixture of all of the above) is used as a mixtureto be separated. Utilization of natural products is rapidly extending inthe various fields such as energy, raw materials, medicines, and foods.However, relating techniques frequently have difficulty in separatingnatural products and face high cost and low quality of a product.

1. A method using a deliquescent filter medium for separating a mixture to be separated, the method comprising: a) a step of forming mother liquid crystals from a mother liquid; b) a step of forming deliquored filter crystals by deliquoring the mother liquid crystals; c) a step of forming a crystal-filter layer of the deliquored filter crystals and supplying a mixture to be separated to a surface of the formed crystal-filter layer to separate the mixture to be separated into a passing liquid passing through the crystal-filter layer and a crystal-filter layer supporting wall having holes, and a captured material captured in the crystal-filter layer, the average distance between the holes of the crystal-filter layer supporting wall having holes being longer than the average thickness of the crystal-filter layer to which the mixture to be separated is being supplied; d) a step of melting the crystal-filter layer among the crystal-filter layer and the captured material captured in the crystal-filter layer; and e) a step of separating, by gravity settling, the melted crystal-filter layer and the captured material captured in the crystal-filter layer.
 2. A method using a deliquescent filter medium for separating a mixture to be separated, the method comprising: a) a step of forming filter crystals from a mother liquid; b) a step of forming a crystal-filter layer of the filter crystals and supplying a mixture to be separated to a surface of the formed crystal-filter layer to separate the mixture to be separated into a passing liquid passing through the crystal-filter layer and a crystal-filter layer supporting wall having holes, and a captured material captured in the crystal-filter layer, the average distance between the holes of the crystal-filter layer supporting wall having holes being longer than the average thickness of the crystal-filter layer to which the mixture to be separated is being supplied; c) a step of melting the crystal-filter layer among the crystal-filter layer and the captured material captured in the crystal-filter layer; and d) a step of separating, by gravity settling, the melted crystal-filter layer and the captured material captured in the crystal-filter layer.
 3. An apparatus using a deliquescent filter medium for separating a mixture to be separated, the apparatus comprising: a) a crystal generator which forms mother liquid crystals from a mother liquid; b) a deliquoring device which deliquores the mother liquid crystals to form deliquored filter crystals; c) a separator which forms a crystal-filter layer of the deliquored filter crystals, supplies a mixture to be separated to a surface of the formed crystal-filter layer, and separates the mixture to be separated into a liquid passing through the crystal-filter layer and a crystal-filter layer supporting wall having holes, and a material captured in the crystal-filter layer, the average distance between the holes of the crystal-filter layer supporting wall having holes being longer than the average thickness of the crystal-filter layer to which the mixture to be separated is being supplied; and d) a tank in which the melted crystal-filter layer and the material captured in the crystal-filter layer are separated by gravity settling separation.
 4. An apparatus using a deliquescent filter medium for separating a mixture to be separated, the apparatus comprising: a) a crystal generator which forms filter crystals from a mother liquid; b) a separator which forms a crystal-filter layer of the filter crystals, supplies a mixture to be separated to a surface of the formed crystal-filter layer, and separates the mixture to be separated into a passing liquid passing through the crystal-filter layer and a crystal-filter layer supporting wall having holes, and a material captured in the crystal-filter layer, the average distance between holes of the crystal-filter layer supporting wall having holes being longer than the average thickness of the crystal-filter layer to which the mixture to be separated is being supplied; and c) a tank in which the melted crystal-filter layer and the material captured in the crystal-filter layer are separated by gravity settling separation.
 5. The apparatus according to claim 3, wherein the crystal generator is an in-liquid rotating drum type including a rotating drum mother liquid tank, a rotating drum immersed in the rotating drum mother liquid tank, and a rotating drum scraping blade provided near the outer surface of the rotating drum, so that the mother liquid crystals are formed on the outer surface of the rotating drum, and the mother liquid crystals are scraped with the scraping blade.
 6. The apparatus according to claim 4, wherein the crystal generator is a low-temperature evaporation type including a cooling chamber which cools a gas, a fan which circulates the cooled gas, a humidifier which evaporates the mother liquid at a low temperature in the gas, a rotary ventilation filter which forms crystals from a gas containing the evaporated mother liquid, and a crystal scraping device which separates the crystals from the ventilation filter to form filter crystals.
 7. The apparatus according to claim 3, wherein the deliquoring device is a centrifugal conveyor type including a rotating basket having holes and a rotating screw-shaped scraping blade provided near the inner surface of the basket, so that the mother liquid crystals are charged to the bottom of the rotating basket and are deliquored by rotation centrifugal force of the basket while being moved upward along the inner wall of the rotating basket with the screw-shaped scraping blade, and the deliquored filter crystals are discharged from an upper portion of the basket.
 8. The apparatus according to claim 3, wherein the separator is a filter cloth inverting type separator including a basket having holes and a filter cloth provided inside the basket and rotating together with the basket, so that the mother liquid crystals are charged in the rotating filter cloth and basket to form the crystal-filter layer, the mixture to be separated is supplied to a surface of the formed rotating crystal-filter layer, the supplied mixture to be separated is subjected to an operation of the separator, supply of the mixture to be separated is stopped, and then a capturing crystal-filter layer is separated from the rotating filter cloth by inverting the filter cloth among the rotating filter cloth and basket and discharged from the separator.
 9. The apparatus according to claim 4, wherein the separator is a drum filtration type including a rotating drum having holes, a crystal reservoir provided outside the drum and holding the filter crystals, and a drum scraping blade, so that the crystal-filter layer is formed by reducing pressure in small chambers which are provided inside a surface material of the drum and which communicate with the holes when the drum passes through the crystal reservoir, the mixture to be separated is supplied to the formed crystal-filter layer and is subjected to an operation of the separator, the supplied mixture to be separated is separated into the passing liquid passing through the crystal-filter layer and the crystal-filter layer supporting wall having holes due to the holes of the drum under reduced pressure and the material captured in the crystal-filter layer, and the capturing crystal-filter layer is separated from the outer surface of the drum with the drum scraping blade due to rotation of the drum.
 10. The apparatus according to claim 3, wherein the crystal generator includes a rotating drum mother liquid tank, a rotating drum immersed in the rotating drum mother liquid tank, and a rotating drum scraping blade provided near the outer surface of the rotating drum, so that the mother liquid crystals are formed on the outer surface of the rotating drum and scraped with the scraping blade; the deliquoring device includes a rotating basket having holes and a rotating screw-shaped scraping blade provided near the inner surface of the basket, so that the mother liquid crystals are charged to the bottom of the rotating basket and are deliquored by rotation centrifugal force of the basket while being moved upward along the inner wall of the rotating basket with the screw-shaped scraping blade, and the deliquored filter crystals are discharged from an upper portion of the basket, and the separator includes a basket having holes, and a filter cloth provided inside the basket and rotating together with the basket, so that the mother liquid crystals are charged in the rotating filter cloth and the basket to form the crystal-filter layer, the mixture to be separated is supplied to a surface of the formed rotating crystal-filter layer, the supplied mixture to be separated is subjected to an operation of the separator, supply of the mixture to be separates is stopped, and then a capturing crystal-filter layer is separated from the rotating filter cloth by inverting the filter cloth among the rotating filter cloth and the basket and discharged from the separator.
 11. The apparatus according to claim 4, wherein the crystal generator includes a cooling chamber which cools a gas, a fan which circulates the cooled gas, a humidifier which evaporates the mother liquid at a low temperature in the gas, a rotary ventilation filter which forms crystals from a gas containing the evaporated mother liquid, and a crystal scraping device which separates the crystals from the ventilation filter to form filter crystals; and the separator includes a rotating drum having holes, a crystal reservoir which is provided outside the drum and which holds the filter crystals, and a drum scraping blade, so that the crystal-filter layer is formed by reducing pressure in small chambers provided inside a surface material of the drum and communicating with the holes when the drum passes through the crystal reservoir, the mixture to be separated is supplied to the formed crystal-filter layer and is subjected to an operation of the separator, the supplied mixture to be separated is separated into the passing liquid passing through the crystal-filter layer and the crystal-filter layer supporting wall having holes due to the holes of the drum under reduced pressure and the material captured in the crystal-filter layer, and a capturing crystal-filter layer is separated from the outer surface of the drum with the drum scraping blade due to rotation of the drum.
 12. A system using a disk-type centrifugal separator for increasing the purity of the passing liquid produced from the separator according to claim
 3. 13. A system using a disk-type centrifugal separator for increasing the purity of a high-viscosity liquid produced by gravity settling separation after melting of the crystal-filter layer according to claim
 4. 14. A system using a disk-type centrifugal separator for increasing the purity of a solid produced by gravity settling separation after melting of the crystal-filter according to claim
 3. 15. A system using a disk-type centrifugal separator for increasing the purity of the passing liquid produced from the separator according to claim
 4. 16. A system using a disk-type centrifugal separator for increasing the purity of a high-viscosity liquid produced by gravity settling separation after melting of the crystal-filter layer according to claim
 4. 17. A system using a disk-type centrifugal separator for increasing the purity of a solid produced by gravity settling separation after melting of the crystal-filter layer according to claim
 4. 18. A system using a disk-type centrifugal separator for increasing the purity of a high-viscosity liquid produced by gravity settling separation after melting of the crystal-filter layer according to claim
 10. 19. A system using a disk-type centrifugal separator for increasing the purity of the passing liquid produced from the separator according to claim
 11. 20. A system using a disk-type centrifugal separator for increasing the purity of a solid produced by gravity settling separation after melting of the crystal-filter layer according to claim
 11. 